Occasionally, under a combination of circumstances, a growth of black, dark brown, or whitish-gray mold appears on the surface of treated lumber, usually when treatment has been made under warm and humid conditions and the pressure treated lumber has been stored and/or shipped in closepiled stacks with no air ventilation to allow for drying. It does not normally occur on lumber dried to at least outer surfaces of 20-25% moisture content or below. The common molds are generally known as Asperqillus, Penicillium, Trichoderma species and Pullularia species. Chromated copper arsenate (CCA) is a known wood preservative that is ineffective against these surface molds.
Chromated copper arsenate is a highly acidic, strongly oxidizing material that is difficult to combine with organic compounds. In this regard, U.S. Pat. No. 3,080,212 to Oberley et al describes, at column 1, lines 64-72, the reaction of reducing sugars with CCA to form difficulty soluble salts as sludge or precipitate, and U.S. Pat. No. 3,416,933 to Nicholson et al discusses, at column 2, lines 30-34, certain wax emulsions that were too unstable in the presence of CCA to be of practical use. Also reactive with CCA are organic fungicides such as sodium pentachlorophenate. Reactivity of organic compounds with CCA can contribute to working solution sludge, and to precipitate deposits on treated wood. Working solution sludge can result even if wood is treated with a CCA-reactive organic compound such as an organic fungicide, long before CCA application.
Chromated copper arsenate has been found to be compatible with certain types of organic compounds. In U.S. Pat No. 4,313,976, CCA is combined with a benzene or naphthalene derivative compound having hydroxy, amino or sulfonic acid functional groups attached to a ring carbon atom. In the Nicholson et al patent, CCA is combined with a hydrophobic wax and a non-ionic surface active agent typically of the long chain fatty alcohol ethylene oxide condensate-type or of the alkyl phenol ethylene oxide condensate-type.
Certain halogenated benzene dinitriles are useful as fungicides on plants, fungus-infested soil, or fungal spores. This art is exemplified by U.S. Pat. Nos. 3,290,353 to Battershell et al, 3,331,735 to Battershell et al, 3,948,636 to Marks, 3,968,239 and 4,177,288, with 3,290,353 broadly describing fungicidal use on "other material to be protected." In U.S. Pat. No. 4,303,668 to Hasegawa, a halogenated benzene dinitrile in combination with an antibacterial and antifungal agent that is dehydroacetic acid, sorbic acid or the alkali metal salts, is said to have a number of fungicidal uses such as on wood (column 4, lines 11-19). In a Diamond Shamrock Product Bulletin on Nopcocide N-40-D (tetrachloroisophthalonitrile), use of a halogenated benzene dinitrile in aqueous paint systems is described. This bulletin also mentions stability of a particular halogenated benzene dinitrile in acidic aqueous media.
However, this art and all prior art of which I am aware, does not show that CCA is compatible with an organic nitrile, in particular with a biodegradable halogenated benzene dinitrile that I have found to be useful in protecting wood against surface molds, and thus fails to provide a wood-treating composition effective against surface molds, containing CCA in combination with a halogenated benzene dinitrile, and further fails to provide treated wood having applied thereto CCA and a halogenated benzene dinitrile.